1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the invention relates to apparatus and methods for independently delivering a plurality of stents or stent segments within a body lumen.
Stenting has become an increasingly important treatment option for patients with coronary artery disease. Stenting involves the placement of a tubular prosthesis within a diseased coronary artery to expand the arterial lumen and maintain the patency of the artery. Early stent technology suffered from problems with restenosis, the tendency of the coronary artery to become re-occluded following stent placement. In recent years, however, improvements in stent design and the advent of drug-eluting stents have reduced restenosis rates dramatically. As a result, the number of stenting procedures being performed in the United States, Europe, and elsewhere has soared.
Stents are delivered to the coronary arteries using long, flexible vascular catheters, typically inserted through a femoral artery. For self-expanding stents, the stent is simply released from the delivery catheter, and it resiliently expands into engagement with the vessel wall. For balloon expandable stents, a balloon on the delivery catheter is expanded which expands and deforms the stent to the desired diameter, whereupon the balloon is deflated and removed.
Despite many recent advances in stent delivery technology, a number of shortcomings still exist. For example, current stent delivery catheters are not capable of customizing the length of the stent in situ to match the size of the lesion to be treated. While lesion size may be measured prior to stenting, using angiography or fluoroscopy, such measurements may be inexact. If a stent is introduced that is found to be of inappropriate size, the delivery catheter and stent must be removed from the patient and replaced with a different device of correct size. Moreover, current stent delivery devices cannot treat multiple lesions with a single catheter. If multiple lesions are to be treated, a new catheter and stent must be introduced for each lesion to be treated.
Additionally, currently available stent delivery devices are not well-adapted for treating vascular lesions that are very long and/or in curved regions of a vessel. Current stents have a discrete length that is relatively short due to their stiffness. If such stents were made longer, to treat longer lesions, they would not conform well to the curvature of vessels or to the movement of vessels on the surface of the beating heart. On the other hand, any attempt to place multiple stents end-to-end in longer lesions is hampered by the inability to maintain appropriate inter-stent spacing and to prevent overlap of adjacent stents. Such shortcomings in the prior art are addressed by the inventions described in U.S. patent application Ser. No. 10/412,714, entitled “Apparatus and Methods for Delivery of Multiple Distributed Stents,” filed on Apr. 10, 2003; and U.S. patent application Ser. No. 10/637,713, entitled “Apparatus and Methods for Delivery of Multiple Distributed Stents,” filed on Aug. 8, 2003; both applications assigned to the assignee of the present invention, and both applications being hereby incorporated fully by reference.
Even with improvements such as those described in the above-referenced patent applications, further improvements in stent delivery devices and methods are still being sought. For example, it may often be advantageous to have stents or stent segments mounted to an expandable deployment member, such as a balloon, at fixed positions along the balloon rather than being slidable along the balloon. This would lock in the relative positions of the stent segments to avoid overlap, excessive spacing, rotational misalignment during deployment, possible damage to the balloon or stent coatings and the like. Stent segments fixed to a balloon would also eliminate the need for a stent pusher to advance the stent segments distally, thereby reducing the profile, stiffness and complexity of the stent delivery catheter. Although conventional stenting devices have a stent pre-mounted to a balloon, currently available fixed-stent deployment devices typically only allow a single stent of fixed length to be deployed at once. It may be desirable, however, to tailor the length of the stent to match the size of the lesion being treated. It may also be desirable to deploy additional stents in one or more subsequent deployments without removing the catheter from the body. It may also be useful to deploy different sizes or types of stents during the same intervention, use different portions of an expandable member having different sizes or shapes, or select other characteristics of each stent deployed in the same intervention. These options are not provided by currently available pre-mounted stent delivery devices.
Therefore, a need exists for improved stent delivery devices and methods. Ideally, such devices and methods would reduce or eliminate the need for sliding stents along an expandable member such as a balloon. Also ideally, such devices and methods would allow for selective deployment of one or more stent segments of a stent. Such devices and methods should also allow in situ customization of stent size, shape, length, material, coating, and other characteristics to match the lesion being treated. Such devices and methods would also ideally be more easily manufactured and used than sliding-stent delivery devices. At least some of these objectives will be met by the present invention.
2. Description of the Background Art
U.S. patent application Ser. Nos. 10/412,714 and 10/637,713, previously incorporated by reference, describe apparatus and methods for delivery of multiple distributed stents. U.S. Pat. Nos. 6,485,510 and 6,258,117 to Camrud et al. describe segmented stents with breakable connections between the segments. U.S. Patent Application Publication No. 2002/0156496 (inventor Chermoni) describes a catheter for carrying stents including a stent positioner. U.S. Pat. No. 6,143,016 to Bleam et al. describes a stent delivery sheath. U.S. Pat. No. 5,807,398 to Shaknovich describes a shuttle stent delivery catheter. U.S. Pat. No. 5,571,036 (Kaplan et al.) and U.S. Pat No. 5,776,141 (Klein et al.) describe an expandable sleeve for placement over a balloon catheter for the delivery of one or two stent structures to the vasculature. U.S. Pat. No. 5,697,948 to Marin et al. describes a catheter for delivering stems covered by a sheath. Patent application Ser. Nos. 2003/0139797 (Johnson) and 2003/0114919 (McQuiston) describe covered segmented stents.